The entire disclosures of Japanese Patent Application Nos. 2007-078423, filed Mar. 26, 2007, 2007-078424, filed Mar. 26, 2007, 2007-078425, filed Mar. 26, 2007, and 2007-020340, filed Jan. 31, 2008 are expressly incorporated herein by reference.
1. Technical Field
The present invention relates to a liquid ejecting apparatus. More specifically, the present invention relates to a liquid ejecting apparatus capable of ejecting a liquid from a liquid ejecting head onto a medium transported through the liquid ejecting apparatus via transport belts.
2. Related Art
One type of liquid ejecting apparatus currently used in the related art is a fixed head ink jet printer which is capable of performing a printing process by transporting a printing medium by electrostatically attracting the printing medium to a transport belt, and discharging ink droplets onto the medium as it is transported by the transport belt. The ink droplets are discharged from rows of nozzles that are formed in the ejecting head in a direction along the width of the transport belt that is orthogonal to the transport direction.
In general, ink jet printers perform maintenance operations to prevent the nozzles from clogging. During one typically maintenance operation that is periodically performed, the ink jet printer performs a flushing operation wherein the ink jet heads is moved toward a head recovery unit provided around the transport belt, below the ink jet heads, by discharging ink droplets from all the nozzles in the ink jet heads. In another cleaning operation, the head recovery unit is moved to bring the caps into contact with the nozzle surface of the ink jet head, wherein the ink is sucked from the ink jet head. In addition, when printing is not being performed, the ink jet printer performs a capping operation wherein the caps are brought into contact with the nozzle surface of the ink jet head in order to close the nozzles.
However, such embodiments, when a printing operation is interrupted in order to perform the flushing or cleaning operation, the head recovery unit returns to the position close to the transport belt, wherein printing is resumed. Because the flushing or cleaning operation is periodically performed, the efficiency of printing is likely to deteriorate. Further, when printing starts during the capping operation, it is necessary to move the ink jet heads from the position close to the transport belts to the upper side of the transport belts. In this case, the time required to start printing is increased, lowering the efficiency of the printing operation.
In order to improve the efficiency of printing, a structure has been proposed in Japanese Patent Application No. JP-A-2005-67127, wherein a plurality of upstream transport belts and a plurality of downstream transport belts with relatively narrow widths are arranged in a zigzag pattern. The plurality of upstream ink jet heads are arranged above the upstream transport belts so as to be interposed between the upstream transport belts, while a plurality of downstream ink jet heads are arranged above the downstream transport belts so as to be interposed between the downstream transport belts. During flushing operations, ink droplets are discharged onto regions of the printing medium between the upstream transport belts and downstream transport belts without moving the ink jet heads or head recovery unit. During a cleaning or capping operation, the head recovery unit provided between the transport belts moves up, without moving the ink jet head, in order to bring the caps into close contact with the nozzle surface of the ink jet head in order to cap the nozzles or suck ink from the ink jet heads.
While, the disclosed ink jet printer is capable of improving the efficiency of the printing process, it is difficult to keep regions of the printing medium onto which ink droplets are discharged from moving since the regions are positioned between the upstream transport belts or the downstream transport belts during the printing operation. This causes difficulties for example, when the distance between the ink jet head and the printing medium varies, making it difficult to accurately land ink droplets to target positions on the printing medium. As a result, image blur or distortion occurs, and image quality is lowered.